The present invention relates in general to a method for fabricating a semiconductor structure including a silicate interface between a silicon substrate and monocrystalline metal oxides, and more particularly to a method for fabricating an interface including a seed layer utilizing atomic layer deposition or atomic layer epitaxy.
A stable silicon (Si) surface is most desirable for subsequent epitaxial growth of metal oxide thin films on silicon for numerous device applications, e.g., ferroelectrics or high dielectric constant oxides for non-volatile high density memory and next generation MOS devices. It is pivotal to establish a stable transition layer on the Si surface for the subsequent growth of monocrystalline high-k metal oxides.
Some reported growth of these oxides, such as BaO and BaTiO3 on Si(100) were based on a BaSi2 (cubic) template by depositing one fourth monolayer of Ba on Si(100) using molecular beam epitaxy at temperatures greater than 850xc2x0 C. See for example: R. McKee et al., Appl. Phys. Lett. 59(7), pp. 782-784 (Aug. 12, 1991); R. McKee et al., Appl. Phys. Lett. 63(20), pp. 2818-2820 (Nov. 15, 1993); R. McKee et al., Mat. Res. Soc. Symp. Proc., Vol. 21, pp. 131-135 (1991); U.S. Pat. No. 5,225,031, issued Jul. 6, 1993, entitled xe2x80x9cPROCESS FOR DEPOSITING AN OXIDE EPITAXIALLY ONTO A SILICON SUBSTRATE AND STRUCTURES PREPARED WITH THE PROCESSxe2x80x9d; and U.S. Pat. No. 5,482,003, issued Jan. 9, 1996, entitled xe2x80x9cPROCESS FOR DEPOSITING EPITAXIAL ALKALINE EARTH OXIDE ONTO A SUBSTRATE AND STRUCTURES PREPARED WITH THE PROCESSxe2x80x9d. A strontium silicide (SrSi2) interface model with a c(4xc3x972) structure was proposed. See for example: R. McKee et al., Phys. Rev. Lett. 81(14), 3014 (Oct. 5, 1998). However, atomic level simulation of this proposed structure indicates that it likely is not stable at elevated temperatures.
Growth of SrTiO3 on silicon (100) using an SrO buffer layer has been accomplished. See for example: T. Tambo et al., Jpn. J. Appl. Phys., Vol. 37 (1998), pp. 4454-4459. However, the SrO buffer layer was thick (100 xc3x85), thereby limiting application for transistor films, and crystallinity was not maintained throughout the growth.
Furthermore, SrTiO3 has been grown on silicon using thick oxide layers (60-120 xc3x85) of SrO or TiOx. See for example: B. K. Moon et al., Jpn. J. Appl. Phys., Vol. 33 (1994), pp. 1472-1477. These thick buffer layers would limit the application for transistors.
Monocrystalline high-k oxides are of great importance for the next generation MOSFET applications. In this context, the term xe2x80x9cmonocrystallinexe2x80x9d shall have the meaning commonly used within the semiconductor industry. The term shall refer to materials that are a single crystal or that are substantially a single crystal and shall include those materials having a relatively small number of defects such as dislocations and the like as are commonly found in substrates of silicon or germanium or mixtures of silicon and germanium and epitaxial layers of such materials commonly found in the semiconductor industry. Typically, in all of these known structures, they are prepared using molecular beam epitaxy (MBE), pulsed laser deposition (PLD), sputtering, and/or metal-organic chemical vapor deposition (MOCVD). In these types of methods of preparation, it is difficult to control the silicon oxide interface to achieve low density of interfacial traps, low leakage current, and for thickness and composition uniformity over large areas, such as 8xe2x80x3 and above, and conformity over trenches. Accordingly, there is a need for a method that provides for a better interface between a silicon substrate and the metal oxide layer, that is conducive to the nucleation of a monocrystalline metal oxide layer, simple to manufacture, controllable, has suppressed fringing effects in MOSFET devices, and suitable for mass production.
Accordingly, it is a purpose of the present invention to provide for a method of fabricating a thin, monocrystalline stable silicate interface with silicon which would allow for the nucleation of a monocrystalline metal oxide layer on silicon.
It is yet another purpose of the present invention to provide for a method of fabricating a semiconductor structure including a monocrystalline metal oxide interface with silicon that is reliable and amenable to high throughput manufacturing.
The above problems and others are at least partially solved and the above purposes and others are realized in a method of fabricating a semiconductor structure including the steps of providing a silicon substrate having a surface, forming on the surface of the silicon substrate, by atomic layer deposition (ALD), a seed layer comprising a silicate material and forming, by atomic layer deposition (ALD) one or more layers of a monocrystalline high dielectric constant oxide on the seed layer.